The documents suggest that the application would not be ready in time to meet a June 30 deadline to be sent to the Nuclear Regulatory Commission but might be substituted at some point in place of a version that the Energy Department knows to be flawed, Loux said.

Loux said other documents suggest that new science teams the Energy Department brought in last fall from Sandia National Laboratories found new problems in engineering and data management.

"It might be a bait and switch," Loux said.

"We found documents that suggest the current performance assessment is largely indefensible."

"We are concerned and disturbed by this," Loux said, adding that at this point the state is operating on suspicion and wants the situation investigated further.

Loux outlined the state's views in a letter sent Monday to Dale Klein, chairman of the Nuclear Regulatory Commission. It was posted Wednesday on the state's Web site.

Asked for comment, Energy Department spokesman Allen Benson wrote in an e-mail to the Stephens Washington Bureau: "The license application will meet NRC requirements." He did not directly address the state's suspicions.

As part of Nevada's efforts to kill the project, state-hired lawyers and engineers are combing thorough a trove of documents that the Energy Department has posted on a Yucca Mountain Web site.

The reviewers look for clues as to the Energy Department's plans and search for ammunition that can be used against the repository, which most state leaders believe will be unsafe and do not want to see built.

In this case, Loux said, the state has discovered references to a "next generation performance assessment" that the Energy Department would refer to after its license request is filed next summer.

"DOE is developing an altogether different version that it considers more defensible but which will not be ready in time," Loux told Klein.